Method of fabricating a heating element



H. H. WILLIAMS METHOD OF FABRICATING A HEATING ELEM Dec. 29, 1970 ENTFiled Oct. 9, 1967 lllm" INVENTOR HARRY H. WILLIAMS United States PatentO 3,550,267 METHOD OF FABRICATING A HEATING ELEMENT Harry H. Williams,400 E. Adams St., Muncie, Ind. 47905 Filed Oct. 9, 1967, Ser. No.673,588 Int. Cl. Hb 3/28 U.S. Cl. 29-611 6 Claims ABSTRACT OF THEDISCLOSURE A method of fabricating a heating element having a base-sheetof fire resistant material, and an electrical cable assembly formed by adoubled over length of heating wire having a loop end and two halvesextending therefrom to two free ends connected to non-heating electricallead conductors.

BACKGROUND OF THE INVENTION It has heretofore been proposed topre-assernble for installation in buildings a radiant heating panelformed of gypsum board or the like having substantially plane front andrear faces and provided in its rear face with a repeatedly retrovertedgroove containing a length of resistance wire. In one form of such apanel, shown in Patent 3,095,491, to G. P. Deacon, the ends of theresist ance wire are connected, at the time of installation, to thenon-heating conductors of a two-wire cable at points within the groove,while in another, shown by my prior Patent 3,277,273, the ends of theresistance wire are connected at the time of installation to appropriatenonheating leads at points outside the panel. In the conventional mannerof making such panels, the groove and Wire must be of matching lengths,and the resistance wire is laid in the panel groove by starting with oneend of the wire at one end of the groove working progressively along thelength of the groove and wire until the other end is reached.Thereafter, the connections to the leads are made.

Soldered connections between the resistance wire and its leads are notpermitted, and it is common practice to insert the end of the resistancewire and an end of its lead into opposite ends of a tubular metalconnector which is then crimped or staked to effect the electricalconnection. A sleeve of insulating material is placed over theconnector. A connection of this general type is shown in the aforesaidDeacon patent. Building codes generally require that connections soeffected carry the approval of Underwriters Laboratories, Inc., hencethey must be made in a factory where they can be inspected by anUnderwriters inspector, and cannot be made at the installation site. Asa result, the heating panels, with the resistance wire in place and withthe leads connected are commonly preassebled into units, and such unitsshipped as such to the site of installation.

Transportation costs place a practical limit on the distance between theplace where such units are manufactured and the place where they are tobe installed. The problem thus presented cannot be readily solved bymultiplying manufacturing sites, as it is impractical to establish theconditions to secure Underwriters approval at a multiplicity of smallfactories scattered throughout the country. My present invention makesit possible to assemble radiant heating panels at scattered convenientlocations without incurring excessive transportation costs, while fullysatisfying requirements for Underwriters approval.

SUMMARY OF THE INVENTION In accordance with the invention, an electricalresistance wire is cut to predetermined length to give the deice siredresistance heating characteristics, and its ends are connected bycrimped connectors or by other means meeting Underwriters requirements,to appropriate leads which are preferably the two conductors of atwo-wire, flexible cable of approved type. Conveniently, the resist ancewire is doubled over at its mid-point and its two ends brought intojuxtaposition before the connections to the leads are made. The assemblyof the doubled-over resistance wire and connected lead cable is thenwound as a continuous unit into a coil, preferably on a spool or reel,with the cable arranged to be unwound first. Coils thus prepared aresuitable to receive Underwriters approval as such, and may bedistributed to manufacturing plants for assembly into complete panelswithout need for fur ther Underwriters approval to satisfy buildingcodes. When the wire assembly is installed in a grooved panel, thewire-receiving grooves in the panel are formed in a serpentine pattern,and preferably in a pattern of parallel grooves wherein each point alongthe groove for one half of the heating wire, as measured from the leadend, is disposed in parallel with the corresponding point of the groovefor the other half. The wire assembly is installed in the groove bystarting with the lead end and working progressively toward the doubledbight in the wire. A cross-connection groove is cut between the parallelgrooves to receive the bight, as the installation is completed.

BRIEF DESCRIPTION OF THE DRAWING The accompanying drawing illustratesthe invention. In such drawing:

FIG. 1 is a plan view of the rear face of a heating panel in which isinstalled a heating cable assembly in accordance with my invention;

FIG. 2 is a perspective view of a lead-retaining cl1p shown in FIG. 1;and

FIG. 3 is a perspective view of my heating cable assembly partiallywound on a spool in accordance with my invention.

DESCRIPTION OF THE PREFERRED EMBODIMENT In the construction shown inFIG. 1, a doubled over length of electrical heating wire 10 has its freeends 12 brought into juxtaposition and connected to the two wires 18 ofa cable 14, and such assembly is installed in a heating panel 16. Thetwo wires 18 of the cable 14 are each enclosed in insulation and areheld together by an additional insulating sheath 20. The heating wire isconnected to the lead conductors by insulated clips 26. The panel 16comprises a rectangular sheet of gypsum board, plaster board, or likefire resistant material, the rear face 22 of which is provided with acontinuous serpentine groove 24 for the reception of the heating wire 10and of short lengths of the lead conductors and the connectors 26 whichjoin the ends of the heating wire to the conductors 18. Preferably abacking sheet 28 of paper or metal foil is applied to the rear face ofthe panel after the heating wire has been installed. The connectors 26are conveniently disposed near an edge of the panel and the two-wirecable 14 emerges at the middle of one edge of the panel. At suchemergence, the panel may be reinforced with a clip 30, shown inperspective in FIG. 2. The clip 30 is formed of a rigid material and hasa body portion 32 and a pair of spaced apart fingers 34 extending fromone end thereof which are bent to embrace the edge of the panel to helphold the clip in place. The clip portion is fixed to the panel as by anadhesive or by a tack passed through a hole 36 in the clip and into thepanel. The cable emerges from the panel between the fingers of the clipwhich adds support to the edge of the board and prevents damage thereto.

The serpentine groove 24 in which the heating wire lies is preferablyformed, as shown, in a pattern of a pair of spaced parallel channels,where any point, as measured from one end of the groove, is adjacent butspaced apart from a point along the groove as measured from the otherend. Both halves of the heating wire 10 are inserted at the same time inthe parallel grooves 24 starting with the lead conductors 18 and workingprogressively toward the doubled bight 38. It is a simple matter to cuta cross connection 39 between the parallel grooves at a point to receivethe bight 38 of the heating wire as the wire insertion is completed.Such cross-connection 39 can be cut at any point, such as at 39' shownin dotted lines, to suit the position of the bight 38 when the rest ofthe wire has been installed.

For shipment and to facilitate installation, the preassembly ofdoubled-over wire 10 and the connected leads 18 of the cable 14 is woundin a package or on a spool in the arrangement shown in FIG. 3. As shown,the assembly is partially wound onto a spool 40, with the midpoint orbight 38 of the doubled-over heating wire wound first on the spool 40 sothat it will be the last portion of the assembly to be unwound, and withthe lead end or cable 14 of the assembly wound last on the spool so thatit will be the first portion to be unwound.

Installation of the heating wire assembly is conveniently accomplishedby pressing the connectors into the groove 24 adjacent the edge of thepanel and adjacent the clip 30. Both halves of the heating wire are thenpressed into the groove concurrently, either by machine or manuallywhile the wire is drawn progressively from the spool or coil. When themid-point 38 of the wire is reached an additional groove may be cut, asneeded, to allow the wire to be pressed into the panel.

The wire assembly may also be installed in other ways than by insertionin a pre-cut groove; for example, it may be stapled to a wall or ceilingsurface. The preassembled heating unit in accordance with the inventionwill provide corresponding advantages in any such other method ofinstallation, in that the installation will start with the lead end ofthe assembly, and progress lengthwise along both halves of the doubledover wire simultaneously. The location of the bight will be variable tosuit the convenience of the installation.

There will be no need to plan ahead to bring the end of the wire to anyparticular location, as is the case when the installer worksprogressively from one end of a wire to the other. The doubled wire canbe unwound from the package as the installation proceeds, and it willnot be be necessary to unwind the entire wire first in order to locatethe remote end.

I claim:

1. A method of fabricating a heating element having a base-sheet of fireresistant material, and a heating cable assembly formed by a doubledover length of heating wire having a loop end and two halves extendingtherefrom to two free ends connected to non-heating electrical leadconductors, comprising locating the two lead conductors at a desiredterminal point on the sheet and, starting at their points of connectionto said conductors, securing both halves of the heating wire inlaterally spaced relation to the sheet progressively from their leadconnected ends to their loop end.

2. The method as set forth in claim 1 wherein the fire resistant sheethas plane front and rear faces and has a serpentine groove in its rearface, further comprising disposing the two halves of the heating wire inparallel with each other while performing the securing step, and whereinthe securing step comprises pressing the heating Wire into theserpentine groove.

3. As an intermediate product for use in constructing the combination ofa resistance heating wire and a supporting base to which the wire is tobe attached in laterally spaced stretches, a heating cable assembly,comprising a doubled over length of electrical heating wire having aloop end and two free ends, the two halves of the wire being arranged inparallel and laterally separable with their free ends being injuxtaposition and permanently connected to non-heating, flexible leadconductors, said assembly, including the doubled over heating wire andsaid conductors, being coiled in a multiturn package from which it isadapted to be progressively removed, the lead conductors beingpositioned in the coil to be removed first and the looped end beingpositioned to be removed last.

4. A heating cable assembly as set forth in claim 3 wherein said leadconductors are the conductors of an insulated cable, said cable havingan insulating sheath surrounding both said conductors.

5. The heating cable assembly as set forth in claim 3, furthercomprising a spool upon which said heating cable assembly is woundbeginning at the looped end of the electrical heating wire.

6. A radiant heating panel comprising a sheet of fire resistant materialhaving substantially plane front and rear faces, the rear face having agroove therein for the reception of a heating wire, a heating cableassembly comprising a doubled over length of electrical heating wirehaving a loop end and parallel halves leading to two free ends, and apair of insulated electrical conductors connected respectively to thefree ends of said heating wire, the heating wire being disposed withinsaid groove and the electrical conductors emerging from the panel forconnection to a source of electric current, said groove comprising twoparallel channels of serpentine form and the two halves of the heatingwire being disposed in parallel along said channels.

References Cited UNITED STATES PATENTS 2,864,931 12/1958 Stoddard et al.219-535 2,915,615 12/1959 Leipold et a1. 219516 3,062,940 11/1962 Baueret al 219-544 3,095,491 6/1963 Deacon 219345 2,824,209 2/1958 Leipold219-528 2,905,918 9/1959 Wagner, Jr. 338210 3,275,803 9/1966 True 2195353,344,392 9/1967 Briscoe 33963 2,114,396 4/1938 McFarlan et al. 219549X3,277,273 10/1966 Williams 219345 FOREIGN PATENTS 217,080 11/1956Australia 219544 VOLODYMYR Y. MAYEWSKY, Primary Examiner US. Cl. X.R.

UNITED STATES PATENT OFFICE CERTIFICATE OF CORRECTION patent 3,550 ,267Dated December 29 1970 Inventor(s) Harry ams It is certified that errorappears in the above-identified patent and that said Letters Patent arehereby corrected as shown below:

Column 4, line 6, beginning with "3. As an intermediate cancel all toand including "along said channels." in line same column 4. In theheading to the printed specification, line 8, "6 Claims" should read 2Claims Signed and sealed this 17th day of August 1971.

(SEAL) Attest:

EDWARD M.FLETCHER,JR. WILLIAM E. SCHUYLER, Attesting OfficerCommissioner of Paten

